Washington (CNN) -- The U.S. military has inadequate and outdated defenses against internal threats, Defense Secretary Robert Gates said Friday after reviewing a Pentagon report examining the Fort Hood shooting last year.

Gates added that the department has not done enough to adapt to the evolving domestic internal security threat to American troops and military facilities, he said.

As well as the failings to communicate about internal threats to the security of personnel, he said, there was a lack of supervision over Army Maj. Nidal Hasan, the psychiatrist charged in the shootings, which killed 13 and injured 28 more.

Gates said the report also makes "accountability recommendations" for Army personnel who supervised Hasan.

He said the recommendations of the report will be sent to the secretary of the Army for further review. He said he is also directing the assistant secretary of defense for homeland defense, Paul Stockton, to look at how the military can more clearly communicate internal threats in order to improve the security of military personnel.

"It is clear that, as a department, we have not done enough to adapt to the evolving domestic internal security threat to American troops and military facilities that has emerged over the past decade," Gates said.